Loads have been wrapped with packaging material by securing a leading end portion of the packaging material to the load or a turntable clamp, dispensing the packaging material, and providing relative rotation between the load and a packaging material dispenser to cause the load to be enveloped by the packaging material. The relative rotation can be provided several different ways. Either the load can be rotated on a turntable, or the dispenser can be rotated around the stationary load. Wrapping usually employs a web of packaging material as the packaging material.
Semi-automatic wrapping machinery requires the operator to attach a leading end portion of the packaging material to the load. This is typically accomplished by collapsing the leading end portion into a rope, then inserting the rope between the layers of the load or tying the end of the packaging material to the edge of the supporting wood pallet or any suitable outcropping on the load. This attachment must be relatively strong since it provides the resistance to pulling the packaging material from the packaging material dispenser during the initiation of the relative rotation between the load and the packaging material dispenser. The attachment or tying of the packaging material makes packaging material removal more difficult after the load has been shipped to its destination.
Automatic wrapping machines typically use packaging material clamps that grip the packaging material web between two opposed surfaces and use electrical or pneumatic actuators to open and close the clamps. Such packaging material clamps create a “tenting” effect during wrapping due to the distance between the clamp and the load during wrapping, resulting in wasted packaging material and loosely wrapped loads. Such clamps are expensive and may require costly maintenance for the electrical and mechanical actuators.
Other machines have used a vacuum device that uses suction to hold the packaging material. This arrangement grips the packaging material, but requires that the packaging material be placed in a flat manner against the vacuum device in order for the vacuum device to provide its full gripping force on the packaging material. Also, the vacuum device may damage the packaging material if the suction generated is too high, while the packaging material may be pulled off the vacuum device if the suction is too low. Furthermore, the vacuum device may have difficulty gripping a roped portion of the packaging material, where the strength of the packaging material is concentrated.
In light of these drawbacks, there is a need for a method and apparatus for wrapping a load with packaging material that operates as effectively as those previously developed but which can be manufactured at a lower cost.